Clingy Martian dust guilty as charged

THE Mars rover Spirit, now bogged down in the Red Planet’s soil, will need all the power it can muster if NASA scientists manage to get it moving again. So it’s timely that researchers are getting a handle on why dust that collects on the vehicle’s solar panels sticks so stubbornly.

Martian dust is particularly clingy. This was noticed more than a decade ago when surprisingly large amounts stuck to the wheels of NASA’s Sojourner rover. Static electricity was thought to be to blame, but no one could explain how the particles became charged. Now a team led by Keith Forward of Case Western Reserve University in Cleveland, Ohio, have an answer.

The team suspected that electrons could jump back and forth between dust grains as they collide in the wind. Smaller grains would be more likely to retain their extra electrons, giving them a negative charge, while larger grains would be left positively charged. Sure enough, they managed to electrically charge grains of Hawaiian volcanic ash, chosen for its similarity to Martian dust, by blowing them around in a container (Geophysical Research Letters, DOI&colon; 10.1029/2009gl038589).

William Farrell of NASA’s Goddard Space Flight Center in Maryland says this may help to combat the dust – important if people travel to Mars. “If the dust is toxic and you bring it inside [a human habitat] it could be extraordinarily bad.”

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